Novel solution to highly uniform CMP for 45 nm device generation: Integration of single-step Cu CMP and planar etch back of dielectric using anti-corrosive DHF and suppression of galvanic corrosion

摘要

Application of PVD-barrier metal (BM) after the 45 nm generation has been considered difficult from the viewpoints of rather poor BM coverage and Cu filling properties. Therefore, gas deposition methods such as CVD and ALD will be applied. If CVD-BM, for example, is adopted, a BM-CMP process can be omitted because BM becomes thinner and the amount of diffusion to an underlying dielectric layer is reduced (Table 1). In general, towever, BMs that can be deposited by CVD such as Ti and W have the large electric potential differences from that of Cu in a liquid. Therefore, galvanic corrosion in a wet process can be a serious problem Although Ta by ALD has been extensively studied because Ta has a smaller potential difference, galvanic corrosion cannot be avoided owing to the influence of the gas residual in Ta (Fig. 1). Thus, we propose Cu-CMP and anti-corrosive DHF (DHF added anti-corrosive) etch-hack integration that suppresses galvanic corrosion and omits BM-CMP (Fig. 2).